Mechanically Stable Mixed Metal Oxide of Cu and Mn as Oxygen Carrier for Chemical Looping Syngas Combustion

Sajen, Sandra; Singh, Sunit Kumar; Mungse, Pallavi; Rayalu, Sadhana; Watanabe, Kosuke; Saravanan, Govindachetty; Labhasetwar, Nitin

doi:10.1021/acs.energyfuels.6b01433

Cited by 27 publications

(14 citation statements)

References 25 publications

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“…Finally, Figure shows the surface morphology of the Cu–Mn composite oxygen carrier before and after consecutive redox cycles. After the reaction of copper and manganese oxides, the structure of the OC surface is modified, and the surface is smooth . Both the fresh and cycled samples present a porous structure that provides channels for oxygen diffusion, which is important for the redox reaction rates.…”

Section: Resultsmentioning

confidence: 99%

Improvement of the Oxygen Uncoupling Properties of Copper-Based Composite Oxygen Carriers for Chemical Looping Air Separation

Annaland

et al. 2020

Energy Fuels

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To increase the oxygen concentration in the product gas of a chemical looping air separation (CLAS) system, it is important to reduce the oxygen uncoupling temperature of the oxygen carrier (OC). In this paper, it is investigated whether and to what extent the addition of Mn2O3, Co3O4, Pb3O4, and Cr2O3, all of which have oxygen uncoupling propensity according to thermodynamics, to CuO improves the oxygen uncoupling behavior of the mixed-oxide OC at lower temperatures. Using thermogravimetric analyses, it is shown that the oxygen uncoupling temperature of a Cu–Mn composite OC is decreased by approximately 200 °C relative to a Cu OC. In addition, the oxygen transport capacity of this composite OC can reach up to 0.056 g O2/g OC. Density functional theory calculations have been carried out to analyze the changes in reactivity and stability of the mixed-oxide OC. When a Mn3O4(001) surface adsorbs a Cu4O4 cluster, the average bond length of Cu–O in the Cu4O4 cluster increases from 1.983 to 2.047 Å and the charge is transferred from Cu4O4 to Mn3O4(001). Chemical reaction between the cluster and the surface occurs, and Cu–Mn composite oxides are formed after adsorption. Moreover, the adsorption energy is −3.749 eV, which is higher than that of Cu4O4 on a CuO(111) surface (−2.92 eV), and the composite OC has better stability and sintering resistance than the Cu OC. The stability of the composite OC was also investigated at 900 °C under reducing conditions and at 700 °C under oxidizing conditions. The results show that the Cu–Mn/Zr composite OC remains stable over 15 consecutive cycles. Moreover, the Cu–Mn composite does not only reduce the oxygen uncoupling temperature of CuO but it also overcomes thermodynamic limitations of the oxidation of Mn3O4 to Mn2O3, where the redox reaction of the Cu–Mn composite OC can be expressed as follows: Cu x Mn3–x O4 ⇋ Cu x Mn2–x + O2(g). From the results, it can be concluded that Mn2O3 is the most suitable composite oxide to improve the oxygen uncoupling properties of a Cu OC for oxygen uncoupling in the CLAS system.

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Section: Resultsmentioning

confidence: 99%

Improvement of the Oxygen Uncoupling Properties of Copper-Based Composite Oxygen Carriers for Chemical Looping Air Separation

Annaland

et al. 2020

Energy Fuels

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“…Researchers found that the initial oxygen-releasing temperatures of Cu–Mn oxygen carriers were 620–850 °C and the oxygen uptake of this composite oxygen carrier was significantly larger than the oxygen uptake of a Mn-based oxygen carrier. The initial oxygen-releasing temperature is about 200 °C lower than that of a Cu/Zr oxygen carrier. − Thus, a copper and manganese composite oxide can be a good candidate for low-temperature CLAS. However, systematic and detailed studies on the properties and, particularly, reaction kinetics of composite Cu–Mn oxygen carriers are still scarce in the literature.…”

Section: Introductionmentioning

confidence: 99%

Oxygen Uncoupling Property and Kinetics of a Copper Manganese Composite Oxygen Carrier in a Packed-Bed Reactor

Wang

Hua

et al. 2020

Energy Fuels

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Decreasing the reduction temperature of an oxygen carrier is the key to reduce energy consumption further and avoid the operational difficulties of chemical looping air separation (CLAS). The copper manganese composite oxygen carrier with zirconia as an inert binder, which has a relatively low temperature of oxygen uncoupling, was developed. In the packed-bed reactor, effects of several important operating parameters, viz., the feed gas rate, temperature, and inlet oxygen concentration, on the separation reactivity were discussed. At higher reaction temperatures, the reduction reactivity increases but the oxidation reactivity decreases. In comparison to a copper oxygen carrier, the equilibrium oxygen concentration of the copper manganese oxygen carrier is greatly enhanced. High gas flow rates can accelerate the separation reaction. In the reduction step, a lower oxygen concentration leads to a higher reduction reactivity. In the oxidation step, the higher oxidation reactivity requires higher oxygen concentrations. The oxygen uncoupling kinetics was determined by the lnln kinetic method. The separation activation energy was determined at 162.95 kJ mol–1, and the most likely mechanism function is the unreacted shrinking core model (R 2). The main compositions in fresh and oxidized composite oxygen carriers are Cu x Mn3–x O4 and ZrO2. After reduction, the active phase compositions are transformed into Cu x Mn2–x O2. The inert phase of ZrO2 is stable during the redox reaction. The repeated separation capability of the composite oxygen carrier over 20 consecutive redox cycles is high.

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“…as low-cost, environmentally benign oxygen carriers are developed recently that can be used as alternative to the currently available oxygen carriers for CLC [11][12][13][14][15]. These mixed oxides form MnO as one of the products after chemical looping combustion reaction using methane, syngas, etc.…”

Section: Introductionmentioning

confidence: 99%

“…These mixed oxides form MnO as one of the products after chemical looping combustion reaction using methane, syngas, etc. and it provides the structural stability to their reduced co-products, which facilitates the regeneration of these oxygen carriers upon heating in air (self-supported oxygen carrier) [11][12][13]. The developed oxygen carrier showed enhanced CLC activity for methane and syngas combustion in terms of multi-cycle performance, stability, CO 2 -selectivity, etc.…”

Section: Introductionmentioning

confidence: 99%

“…The developed oxygen carrier showed enhanced CLC activity for methane and syngas combustion in terms of multi-cycle performance, stability, CO 2 -selectivity, etc. under harsh CLC operational conditions than that of its counterparts (Cu-, Fe-and Mn-oxides) [11][12][13]. In addition, these oxygen carriers possess CLOU property, which is the tendency of releasing gaseous oxygen from their lattice upon heating [16][17][18].…”

Section: Introductionmentioning

confidence: 99%

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Solvent-free, improved synthesis of pure bixbyite phase of iron and manganese mixed oxides as low-cost, potential oxygen carrier for chemical looping with oxygen uncoupling

Mungse

Saravanan

Nishibori

et al. 2017

Pure and Applied Chemistry

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Chemical looping with oxygen uncoupling (CLOU) is the tendency of releasing gaseous oxygen of an oxygen carrier upon heating, which is the key property for the efficient and cleaner combustion of solid fuels for their wide exploitation for thermal power applications. The solvent-free, improved synthesis method was developed for the synthesis of pure bixbyite, FeMnO 3 (Ia3 ̅ , a = b = c = 0.94 nm) as a low-cost, oxygen carrier by exposing of the abundantly available precursors (Fe 3 O 4 and MnO) under inert-or reduction-atmosphere followed by air at 900 °C. The bixbyite FeMnO 3 showed the enhanced, stable multi-cycle CLOU performance than that of the physical mixture and it is converted into FeMn 2 O 4 after the complete exhaustion of reactive oxygen under CLOU conditions. FeMnO 3 showed the uniform elemental distribution of Fe, Mn and O, which facilitate the regeneration in air upon heating for multi-cycle performance. 3.2 wt.% of reactive oxygen can be obtained compared to the mass of FeMnO 3 which is almost equal to the theoretical value under CLOU conditions. The lattice of FeMnO 3 is altered linearly above 100 °C with the increase of temperature, however; without the decomposition of the bixbyite phase and it was reinstated virtually upon cooling in air.

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Mechanically Stable Mixed Metal Oxide of Cu and Mn as Oxygen Carrier for Chemical Looping Syngas Combustion

Cited by 27 publications

References 25 publications

Improvement of the Oxygen Uncoupling Properties of Copper-Based Composite Oxygen Carriers for Chemical Looping Air Separation

Improvement of the Oxygen Uncoupling Properties of Copper-Based Composite Oxygen Carriers for Chemical Looping Air Separation

Oxygen Uncoupling Property and Kinetics of a Copper Manganese Composite Oxygen Carrier in a Packed-Bed Reactor

Solvent-free, improved synthesis of pure bixbyite phase of iron and manganese mixed oxides as low-cost, potential oxygen carrier for chemical looping with oxygen uncoupling

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